Superconducting and conventional power transmission cable comparison

       

There are many advantages of superconducting underground power transmission cables claimed over conventional copper cables, but none of them carries very far. One claim frequently made is space saving in densely populated urban areas.

Now here you see some superconductor cables on the left and conventional HV and EHV cables of similar power transmission capabilities on the right side.

While you may be used to read that a superconductor can carry 100 times more current per cross section, this is true for the bare conductor. However, even a conventional HV cable has a cross section of which the conductor makes only a fraction. On top of the insulant comes the requirement for a cooling duct and a cryostat (heat isolation) in a superconductor.

Also note the copper conductors inside the superconducting cables! They are needed as emergency conductors, should the superconductivity ever quench.

More copper will be needed for the cooling plant, so without “vintage” copper the superconductor will never work anyway.

It also remains to be doubted whether there is a huge space requirement for power transmission at all, since any sort of cable is quite compact compared to other ducts needed underground. Replacing a conventional waste water tube, which may be more than 1.5 m in diameter, with a “superconducting waste water tube” would be more profitable but has not yet been invented.